Optical film, liquid crystal display device comprising same, and method for manufacturing protective film used therefor

Abstract

An optical film, a liquid crystal display including the same, and a method for manufacturing a protective film used therefor are provided. An optical film includes a polarizer and a protective film laminated or stacked on at least one surface of the polarizer, and a thickness-direction retardation (Re) of the protective film is in the range of 0 nm to 200 nm, and an out-of-plane retardation (Rth) of the protective film is in the range of 300 nm to 1,200 nm.

The invention claimed is: 
     
       1. An optical film comprising:
 a polarizer; and 
 a protective film on at least one surface of the polarizer, 
 wherein the protective film has an in-plane retardation (Re) of 0 nm to 200 nm and an out-of-plane retardation (Rth) of 300 nm to 1,200 nm. 
 
     
     
       2. The optical film according to  claim 1 , wherein the protective film has a thickness of 1 μm to 55 μm. 
     
     
       3. The optical film according to  claim 1 , wherein the protective film comprises a polyester material. 
     
     
       4. The optical film according to  claim 3 , wherein the protective film comprises polyethylene terephthalate, polyethylene naphthalate, or a copolymer comprising polyethylene terephthalate and polyethylene naphthalate. 
     
     
       5. The optical film according to  claim 4 , wherein the protective film has a triple co-extrusion structure comprising polyethylene terephthalate, polyethylene naphthalate, or a copolymer comprising polyethylene terephthalate and polyethylene naphthalate. 
     
     
       6. The optical film according to  claim 1 , further comprising:
 a retardation compensation film on an opposite surface of the polarizer with respect to the at least one surface of the polarizer, on which the protective film is located. 
 
     
     
       7. A liquid crystal display comprising:
 a liquid crystal cell; 
 a backlight unit; 
 a lower polarizing plate between the liquid crystal cell and the backlight unit; and 
 an upper polarizing plate on a visible side of the liquid crystal cell, the upper polarizing plate comprising the optical film according to  claim 1 . 
 
     
     
       8. The liquid crystal display according to  claim 7 , wherein the protective film of the optical film is disposed on a visible side of the upper polarizing plate. 
     
     
       9. The liquid crystal display according to  claim 8 , further comprising:
 a brightness enhancement film between the lower polarizing plate and the backlight unit. 
 
     
     
       10. The liquid crystal display according to  claim 7 , wherein the lower polarizing plate comprises an optical film comprising:
 a polarizer; and 
 a protective film on at least one surface of the polarizer of the optical film of the lower polarizing plate, 
 wherein the protective film of the optical film of the lower polarizing plate has an in-plane retardation (Re) of 0 nm to 200 nm and an out-of-plane retardation (Rth) of 300 nm to 1,200 nm. 
 
     
     
       11. The liquid crystal display according to  claim 10 , wherein the protective film of the optical film of the lower polarizing plate is on a light source side of the lower polarizing plate. 
     
     
       12. The liquid crystal display according to  claim 11 , wherein the protective film of the optical film of the upper polarizing plate is on a visible side of the upper polarizing plate. 
     
     
       13. The liquid crystal display according to  claim 12 , further comprising:
 a brightness enhancement film between the lower polarizing plate and the backlight unit. 
 
     
     
       14. A method of manufacturing a protective film, the method comprising:
 manufacturing a non-stretched polyester film; and 
 stretching the non-stretched polyester film, 
 wherein a stretching ratio (MD:TD) is from 2.0:1.0 to 3.0 to 3.0:2.0 to 4.0.